Multi-winding high sensitivity current transformer

ABSTRACT

A system includes a sensor configured to detect an electrical leakage current associated with an operation of an industrial machine. The sensor includes a core and a first winding encircling a first portion of the core. The first winding includes a first number of turns. The first winding is configured to obtain a set of electrical current measurements associated with the operation of the industrial machine. The sensor includes a second winding encircling a second portion of the core. The second winding includes a second number of turns. The second winding is configured to obtain the set of electrical current measurements associated with the operation of the industrial machine. The first winding and the second winding are each configured to generate respective outputs based on the set of electrical current measurements. The respective outputs are configured to be used to reduce the occurrence of a distortion of the set of electrical current measurements based on a temperature of the core.

The subject matter disclosed herein relates to industrial machines and,more specifically, to systems for monitoring leakage currents that maybe associated with the industrial machines.

Certain synchronous and/or asynchronous machines such as electric motorsand generators may experience leakage currents on the stator windings ofthe machines during operation. Specifically, because the stator windingsmay include metal windings in close proximity, the stator windings ofthe motor may be subject to inherent capacitance (e.g., capacitivecurrent leakage). Electric machines may also experience leakage currentsdue to less than optimal or ineffective insulation protecting the statorwindings (e.g., resistive current leakage). Sensors may be provideddetect the leakage currents. Unfortunately, the sensors may be highlysensitive to ambient and/or operational temperature variations, and maythus generate distorted values for the detected leakage currents.Accordingly, it may be desirable to provide improved sensors fordetecting leakage currents.

BRIEF DESCRIPTION

Certain embodiments commensurate in scope with the originally claimedinvention are summarized below. These embodiments are not intended tolimit the scope of the claimed invention, but rather these embodimentsare intended only to provide a brief summary of possible forms of theinvention. Indeed, the invention may encompass a variety of forms thatmay be similar to or different from the embodiments set forth below.

In accordance with a first embodiment, a system includes a sensorconfigured to detect an electrical leakage current associated with anoperation of an industrial machine. The sensor includes a core and afirst winding encircling a first portion of the core. The first windingincludes a first number of turns. The first winding is configured toobtain a set of electrical current measurements associated with theoperation of the industrial machine. The sensor includes a secondwinding encircling a second portion of the core. The second windingincludes a second number of turns. The second winding is configured toobtain the set of electrical current measurements associated with theoperation of the industrial machine. The first winding and the secondwinding are each configured to generate respective outputs based on theset of electrical current measurements. The respective outputs areconfigured to be used to reduce the occurrence of a distortion of theset of electrical current measurements based on a temperature of thecore.

In accordance with a second embodiment, a non-transitorycomputer-readable medium having computer executable code stored thereon,the code includes instructions to receive a line voltage measurementassociated with a first set of windings and a second set of windingscoiled around a core of a current sensor, receive a plurality ofelectrical leakage current measurements via the current sensor, andcalculate an amplitude and a phase angle of a respective output voltageof each of the first set of windings and the second set of windings. Theamplitude and phase of the respective output voltages are referenced tothe line voltage measurement. The code includes instructions tocalculate a phase-shift angle and a magnetic permeability valuecorresponding to each of the first set of windings and the second set ofwindings based at least in part on the phase angle of the respectiveoutput voltages, and derive one or more correction factors based on thephase-shift angles and the magnetic permeability value. The one or morecorrection factors are configured to correct a temperature-based oraging-based distortion of the electrical leakage current measurements.

In accordance with a third embodiment, a system includes a processorconfigured to receive a line voltage measurement associated with a firstset of windings and a second set of windings coiled around a core of acurrent sensor, to receive a plurality of electrical leakage currentmeasurements via the current sensor, and to calculate an amplitude and aphase angle of a respective output voltage of each of the first set ofwindings and the second set of windings. The amplitude and phase of therespective output voltages are referenced to the line voltagemeasurement. The processor is configured to calculate a firstphase-shift angle corresponding the first set of windings and a secondphase-shift angle corresponding to the second set of windings based atleast in part on the phase angle of the respective output voltages, tocalculate a magnetic permeability value of the core of the currentsensor based at least in part on the phase angle of the respectiveoutput voltages, and to derive one or more correction factors based onthe phase-shift angles and the magnetic permeability value. The one ormore correction factors are configured to correct a temperature-based oraging-based distortion of the electrical leakage current measurements.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a block diagram of an embodiment of a industrial machine andcontrol system including a controller, in accordance with presentembodiments;

FIG. 2 is a block diagram of an embodiment of an equivalent circuit ofthe system of FIG. 1 including a first winding and a second winding, inaccordance with present embodiments;

FIG. 3 is a detailed block diagram of the equivalent circuit of FIG. 2including a signal conditioning circuit, in accordance with presentembodiments; and

FIG. 4 is a flow diagram illustrating an embodiment of a process usefulin correcting temperature-based distortions of detected leakage currentsignals, in accordance with present embodiments.

DETAILED DESCRIPTION

One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

When introducing elements of various embodiments of the presentinvention, the articles “a,” “an,” “the,” and “said” are intended tomean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

Present embodiments relate to a two-winding configuration current sensorthat may be used to provide accurate measures of detected leakagecurrents by, for example, correcting and compensating for the ambientand/or operational temperature variations of the sensor and/ormechanical stress on the core of the sensor. In one embodiment, thesensor may include a high sensitivity current transformer (HSCT).Specifically, the sensor may include a first set of windings with afirst number of turns and second set of windings with a second number ofturns. The first set of windings and the second set of windings may becoiled independently on the core of the sensor, such that the sensorprovides at least two voltage outputs. In one embodiment, the twooutputs may be connected to the input of a signal conditioning circuitwith a multiplexing functionality to ensure that only one signal of thetwo voltage outputs of the sensor is electrically connected andprocessed per time period. Based on the two voltage outputs (and othermeasurements obtained by the current sensor and high voltage sensor) andthe parameters of the sensor, the respective phase-shifts correspondingto the first set of windings and the second set of windings and theinstantaneous permeability (e.g., corresponding to the immediate ambientand/or operational temperature) of the core of the sensor may becalculated and used to compensate for, or correct any errors that mayhave become present, for example, in the detected leakage currents.Moreover, based on the two voltage outputs, and, by extension, therespective phase-shifts of the first set of windings and the second setof windings, an indication as to whether the detected leakage currentsinclude capacitive leakage currents, resistive leakage currents, or acombination of capacitive leakage currents and resistive leakagecurrents may be provided. Indeed, although the present embodiments maybe discussed primarily with respect to a current sensor, it should beappreciated that the techniques described herein may be applied to anycore-based sensor and/or other core-based device.

With the foregoing in mind, it may be useful to describe an industrialmachine and control system, such as an example industrial machine andcontrol system 10 illustrated in FIG. 1. As depicted, the system 10 mayinclude an industrial machine 12 including a number of stator windings14, a number of leakage current sensors 16, 18, and 20, and a number ofvoltage sensors 22, 24, and 25 all communicatively coupled to acontroller 26. The industrial machine 12 may be any single ormulti-phase synchronous, asynchronous, or induction machine useful inconverting an electrical power input into a mechanical output to driveanother system or device. For example, in certain embodiments, theindustrial machine 12 may be a single or multi-phase electric motor, aninduction motor, or, in other embodiments, a generator. Thus, asillustrated, the industrial machine 12 may include the stator windings14. As it may be appreciated, the stator windings 14 may include singleor polyphase conductors (e.g., phases a, b, c) that may be coiled aroundan iron magnetic core to form magnetic poles when energized with anelectrical current. Although not illustrated, it should be appreciatedthat the magnetic field generated by the windings of the stator windings14 may rotate a drive shaft.

As previously noted, a number of leakage current sensors 16, 18, and 20may be communicatively coupled to each of three-phases (e.g., phases a,b, c) of the stator windings 14, and, by extension, the machine 12. Incertain embodiments, the leakage current sensors 16, 18, and 20 mayinclude, for example, high sensitivity current transformers (HSCTs),other current transformers (CTs), or any devices that output a signal(e.g., AC/DC voltage or current) proportional to a detected electricalcurrent flowing through the electrically and/or communicatively coupledphase conductors 27. As also illustrated, a number of voltage sensors22, 24, and 25 may be communicatively coupled to each of thethree-phases (e.g., phases a, b, c) of the stator windings 14, and byextension, the machine 12. The voltage sensors 22, 24, and 25 mayinclude, for example, any of various high voltage sensors (HVSs) (e.g.,high voltage dividers) useful in producing a voltage proportional to adetected voltage on the three-phase conductors 27.

In certain embodiments, the leakage current sensors 16, 18, and 20 maybe communicatively coupled to corresponding leakage current sensorinterface modules 28, 30, and 32 corresponding to each of thethree-phase conductors 27 (e.g., phases a, b, c) of the stator windings14. The leakage current sensor interface modules 28, 30, and 32 may beuseful in processing the outputs of the leakage current sensors 16, 18,and 20 (e.g., on-site), and subsequently delivering the leakage currentsensor outputs to the controller 26. The leakage current sensors 16, 18,and 20 may also include a processor (e.g., microcontroller) to performone or more processing operations on the leakage current sensor outputsbefore transmission of the outputs to the current sensor interfacemodules 28, 30, and 32. Similarly, the voltage sensors 22, 24, and 25may be communicatively coupled to corresponding voltage sensor interfacemodules 34, 35, and 36 corresponding to the three-phase conductors 27(e.g., phases a, b, c) of the stator windings 14. The voltage sensorinterface modules 34, 35, and 36 may be useful in processing the outputsof the voltage sensors 22, 24, and 25 (e.g., on-site), and subsequentlydelivering the voltage sensor outputs to the controller 26. Thus, itshould be appreciated that the current sensor interface modules 28, 30,and 32 and the voltage sensor interface modules 34, 35, and 36 mayinclude one or more processors (e.g., such as a processor 37) and memory(e.g., such as a memory 39) to perform the aforementioned functionsand/or operations.

In certain embodiments, the controller 26 may be suitable for generatingand implementing various control algorithms and techniques to controlthe current and/or voltage of the stator windings 14, and by extension,the output (e.g., speed, torque, frequency, and so forth) of the machine12. The controller 26 may also provide an operator interface throughwhich an engineer or technician may monitor the components of the system10 such as, components (e.g., leakage current sensors 16, 18, and 20 andvoltage sensors 22, 24, and 25) of the machine 12. Accordingly, as willbe further appreciated, the controller 26 may include one or moreprocessors 37 that may be used in processing readable and executablecomputer instructions, and a memory 39 that may be used to store thereadable and executable computer instructions and other data. Theseinstructions may be encoded in programs stored in tangiblenon-transitory computer-readable medium such as the memory 39 and/orother storage of the controller 26. Furthermore, the one or moreprocessors 37 and memory 39 may allow the controller 26 to beprogrammably retrofitted with the instructions to carry out one or moreof the presently disclosed techniques without the need to include, forexample, additional hardware components.

In certain embodiments, the controller 26 may also host variousindustrial control software, such as a human-machine interface (HMI)software, a manufacturing execution system (MES), a distributed controlsystem (DCS), and/or a supervisor control and data acquisition (SCADA)system. For example, in one embodiment, the controller 26 may be a MotorStator Insulation Monitor (MSIM)™ available from General Electric Co.,of Schenectady, N.Y. Thus, the control system may be a standalonecontrol system, or one of several control and/or monitoring systemsuseful in monitoring and regulating the various operating parameters ofthe machine 12. As will be further appreciated, the controller 26 may beused to monitor leakage currents {right arrow over (I_(a,l))}, {rightarrow over (I_(b,l))}, and {right arrow over (I_(c,l))}, and/ordissipation factor (DF) that may be associated with the three-phase(e.g., phases a, b, c) stator windings 14. Specifically, leakagecurrents {right arrow over (I_(a,l))}, {right arrow over (I_(b,l))}, and{right arrow over (I_(c,l))}, may appear in one or more phases of thestator windings 14 in the forms of capacitive leakage currents and/orresistive leakage currents. The total leakage current (e.g., the vectorsum of the capacitive leakage currents and the resistive leakagecurrents) may possibly cause mechanical damage or thermal damage to thestator windings 14 if left to persist.

Turning now to FIG. 2, a block diagram of an embodiment of the sensor 16is illustrated. For the purpose of illustration, henceforth, the sensors16, 18, and 20 may be discussed with respect to only sensor 16 (e.g.,phase a). However, it should be appreciated that the present embodimentsmay be implemented with respect to each of the sensors 16, 18, and 20,or other sensors 16, 18, and 20 that may be present in the system 10.Furthermore, in FIG. 2, at least one of the phases (e.g., phase a) ofthe industrial machine 12 is depicted as an equivalent load 14 and apath in an insulation material is illustrated as an equivalent circuit40, including a capacitance C_(leakage) and a resistance R_(leakage).The system 10 of FIG. 2 may also include an equivalent voltage source41, which may be one phase of a polyphase voltage source (e.g., singleor polyphase grid power) that may be used to provide power to theindustrial machine 12 and/or equivalent load 14.

As previously noted with respect to FIG. 1, the sensor 16 may be anydevice useful in measuring low level leakage current of the machinestator windings 14. Specifically, as in illustrated in FIG. 2, incertain embodiments, the sensor 16 may be a magnetic coil based currenttransducer that includes a core 42 and core windings 44, 46. The core 42of the sensor 16 may include high permeability magnetic materials suchas, for example, high nickel, iron, supermalloy, or other similar highpermeability magnetic materials that may exhibit a high sensitivity tomechanical stress. As will be further appreciated, the sensingfunctionality of the sensor 16 may be very sensitive to ambient and/oroperational temperature variations. Particularly, the thermal effect onthe core windings 44, 46 of sensor 16 may cause the core 42 of thesensor 16 to experience substantial mechanical stress. Indeed, theresponse of the sensor 16 due to the temperature variations, and, byextension, the mechanical stress may be highly nonlinear. This mayresult in the sensor 16 generating distorted leakage current measurementvalues that vary undesirably according to the ambient and/or operationaltemperature of the sensor 16.

Specifically, the sensor 16 may include a highly nonlinear temperatureresponse, and thus the sensor 16 may be very sensitive to ambient and/oroperational temperature variations. In one embodiment, the highlynonlinear temperature variation may be within a specific operatingtemperature range. For example, the signal phase of the voltage outputof the sensor 16 may vary from approximately 20% between 70 C to 0 Cdegree and up to approximately 80% between 0 C to −20 C degree.Specifically, lower ambient temperatures (e.g., cooler or coldtemperatures) may cause the sensor 16 core 42 to contract and experiencesignificant mechanical stress. The core 42 may also experience amaterial change (e.g., a change in molecular and/or devicecharacteristics). This may lead to a decrease in the permeability of themagnetic material of the core 42, and thus decrease the inductance ofthe core windings 44 and 46.

Accordingly, to compensate for the mechanical stress and core materialchange, in certain embodiments, the sensor 16 may include at least twocore windings 44, 46 each coiled around the core 42. The core windings44, 46 may be used to sense and measure leakage current by measuring thedifferential current from electrical power inputs I_(in) and outputsI_(out). Based on the measurements of the vector current inputs I_(in),outputs I_(out) and line voltage, the permeability of the core 42 may becalculated (e.g., calculated by the current sensor interface module 28or other processor that may be included as part of the sensor 16). Thesensor 16 output signal phase-shift may be inversely proportional to thecore windings 44, 46 inductance (e.g., L₁, L₂) and proportional to theloading resistance (e.g., R_(L)).

In certain embodiments, the core windings 44, 46 may be used to measurethe magnitude and phase of the current inputs I_(in) and outputs I_(out)together, measurements that may be corrected for variations due totemperature variations, other thermal effects, and/or aging effects onthe core 42 material (e.g., permeability creeping). Specifically, thewindings 44 may be configured to have a specified number of turns (N₁),and the windings 46 may be configured to have a specified number ofturns (N₂). In certain embodiments, the ratio of the number of turnsbetween the windings 44 and the windings 46 may be a 1.5:1 ratio, 2:1ratio, a 3:2 ratio, a 4:3 ratio, or other ratio in which the number ofturns (N₁) is not equal to the number of turns (N₂). As illustrated, thewindings 44 and the windings 46 may be wound separately andindependently around the core 42 of the sensor 16. Thus, in measuring acurrent, the sensor 16 may give at least two independent voltage outputs(e.g., Output₁ and Output₂).

In certain embodiments, as illustrated in FIG. 3, the Output₁ andOutput₂ (e.g., corresponding to the voltage on the windings 44 and thewindings 46) of the sensor 16 may be each coupled to an input of asignal conditioning circuit 48 (e.g., which may be included within oneor more of the current sensor interface modules 28, 30, and 32) that mayinclude a multiplexing functionality (e.g., multiplexing switches 50) toensure that only one signal of the Output₁ and Output₂ are electricallyconnected and processed at a time. Based on the measurements of Output₁and Output₂ of the sensor 16 and the measured voltage of the voltagesource 41 (e.g., measured by the voltage sensor 22), the instantaneouspermeability (e.g., the permeability corresponding to the immediateambient and/or operational temperature) of the core 42 of the sensor 16may be calculated (e.g., calculated via the current sensor interfacemodule 28 or other processor that may be included as part of the sensor16). The current sensor interface module 28 (or current sensor interfacemodules 30 and 32) may then use the instantaneous permeability tocompensate for any errors that may, for example, become present in thedetected leakage current signals {right arrow over (I_(a,l))}, {rightarrow over (I_(b,l))}, and {right arrow over (I_(c,l))}. Indeed, as willbe further appreciated, based on the measurements of Output₁ andOutput₂, the current sensor interface module 28 (or current sensorinterface modules 30 and 32) may measure a phase-shift (Θ+α)° measuredby the core windings 44, and a phase-shift (Θ+β)° measured by the corewindings 46. Specifically, as will be further appreciated, the currentsensor interface module 28 (or current sensor interface modules 30 and32) may use Output₁ and Output₂ to calculate the specific phase angle Θassociated with the detected leakage current signals {right arrow over(I_(a,l))}, {right arrow over (I_(b,l))}, and {right arrow over(I_(c,l))}, and the specific phase angles α and β associated with phaseshifts that may be introduced by the core windings 44 and 46,respectively. In this way, the current sensor interface module 28 (orcurrent sensor interface modules 30 and 32) may provide an indication asto whether the detected leakage currents {right arrow over (I_(a,l))},{right arrow over (I_(b,l))}, and {right arrow over (I_(c,l))} includescapacitive leakage currents, resistive leakage currents, or acombination of capacitive leakage currents and resistive leakagecurrents.

For example, in certain embodiments, the sensor 16 (or sensors 18 and20) may obtain the leakage current measurements {right arrow over(I_(a,l))}, {right arrow over (I_(b,l))}, and {right arrow over(I_(c,l))}, which may be expressed as:

$\begin{matrix}{\overset{\rightharpoonup}{I_{Leakage}} = {\frac{\overset{\rightharpoonup}{V_{Source}}}{\overset{\rightharpoonup}{Z_{Leakage}}} = {I_{Leakage}\mspace{14mu}\angle\mspace{14mu}{{\Theta{^\circ}}.}}}} & {{equation}\mspace{14mu}(1)}\end{matrix}$

The voltage outputs Output₁ and Output₂ may be then calculated (e.g., byway of one or more of the current sensor interface modules 28, 30, and32 or other processor(s) that may be included as part of the respectivesensors 16, 18, 20) as:{right arrow over (V _(output1))}={right arrow over (H ₁)}×{right arrowover (I _(Leakage))}=H ₁ ∠α°×I _(Leakage) ∠Θ°=V _(Output1)∠(Θ+α)°  equation (2),and{right arrow over (V _(output2))}={right arrow over (H ₂)}×{right arrowover (I _(leakage))}=H ₂ ∠β°×I _(Leakage) ∠Θ°=V _(Output2)∠(Θ+β)°  equation (3).

As noted above, phase angle Θ may be the phase angle of the detectedleakage current {right arrow over (I_(leakage))}. The phase angles α andβ in the above-illustrated equation (2) and equation (3) may representthe respective phase shifts that may be introduced by the core windings44, 46 of the sensor 16 (or sensors 18 and 20) due to, for example,distortions based on the ambient and/or operational temperature and/oraging core of the sensor 16, and, by extension, the mechanical stress onthe core 42 of the sensor 16 (or sensor 18 and 20). Similarly, {rightarrow over (H₁)} and {right arrow over (H₂)} may represent therespective transfer functions used to describe the functionality of thesensor 16 (or sensors 18 and 20) corresponding to the windings 44, 46.Accordingly, based on the transfer functions {right arrow over (H₁)} and{right arrow over (H₂)}, the respective phase-shift angles α and β andthe magnetic permeability (e.g., which may be variable as a function ofthe temperature and age of the core 42) may be then calculated (e.g., byway of one or more of the current sensor interface modules 28, 30, and32 or other processor(s) that may be included as part of the respectivesensors 16, 18, and 20) in accordance with the following equations:

$\begin{matrix}{{{\tan(\alpha)} = {\frac{R_{S_{1}} + R_{L}}{\omega\; L_{1}} = \frac{S_{1}}{\mu}}},{and}} & {{equation}\mspace{14mu}(4)} \\{{\tan(\beta)} = {\frac{R_{S_{2}} + R_{L}}{\omega\; L_{2}} = {\frac{S_{2}}{\mu}.}}} & {{equation}\mspace{14mu}(5)}\end{matrix}$

Thus, the instantaneous permeability μ (e.g., the permeabilitycorresponding to the immediate ambient and/or operational temperatureand age) of the core 42 of the sensor 16 and the phase-shift angles αand β may be calculated based on the independent voltage outputs Output₁and Output₂) detected via the respective core windings 44 and 46 of thesensor 16. Specifically, as illustrated, the phase-shift angles α and βmay be inversely proportional to windings 44 and 46 inductance (e.g.,L₁, L₂) and proportional to the loading resistance (e.g., R_(L)) and thecoil resistance (e.g., R_(S2)) of the sensor 16. The current sensorinput module 28 (or current sensor input modules 30 and 32) may then usethe instantaneous permeability to compensate for, or correct any errorsthat may have become present, for example, in the detected leakagecurrent {right arrow over (I_(Leakage))}. In this way, the sensor 16 (orsensors 18 and 20) may provide accurate measures of the leakage currentsignals {right arrow over (I_(a,l))}, {right arrow over (I_(b,l))}, and{right arrow over (I_(c,l))}, for example, irrespective of the ambientand/or operational temperature or age of the sensor 16 (or sensors 18and 20) and/or the mechanical stress of the core 42 based thereon.Moreover, the current sensor interface module 28 (or current sensorinterface modules 30 and 32) may provide an indication as to whether thedetected leakage current {right arrow over (I_(Leakage))} includes acapacitive leakage current, a resistive leakage current, or acombination of capacitive leakage current and resistive leakage current.

Turning now to FIG. 4, a flow diagram is presented, illustrating anembodiment of a process 52 useful in correcting temperature-based andaging-based distortions of detected leakage current signals, by using,for example, the current sensor interface modules 28, 30, and 32 or oneor more processors that may be included as part of the sensors 16, 18,and 20 included in the system 10 depicted in FIG. 1. The process 52 mayinclude code or instructions stored in a non-transitory machine-readablemedium (e.g., such as the memory 39) and executed, for example, by theone or more the current sensor interface modules 28, 30, and 32 and/orother processing devices. The process 52 may begin with one or more ofthe sensors 16, 18, and 20 obtaining (block 54) leakage currentmeasurements (e.g., leakage current signals {right arrow over(I_(a,l))}, {right arrow over (I_(b,l))}, and {right arrow over(I_(c,l))},) and line voltage measurement. The process 52 may continuewith the one or more current sensor interface modules 28, 30, and 32and/or other processing devices (e.g. included as part of the one ormore sensors 16, 18, and 20) calculating (block 56) the output voltage(e.g., Output₁ and Output₂) of each of a first and second set of corewindings 44 and 46, and determining the phase angles (Θ+α)° and (Θ+β)°(e.g., in reference to the line voltage) of the output voltage (e.g.,Output₁ and Output₂) of each of a first and second set of core windings44 and 46.

The process 52 may then continue with the one or more the current sensorinterface modules 28, 30, and 32 and/or other processing devices (e.g.included as part of the one or more sensors 16, 18, and 20) calculating(block 58) first and second phase-shift angles α° and β° that may beintroduced by the respective windings 44 and 46 and the magneticpermeability value μ of the core 42 based, for example, on therespective output voltages (e.g., Output₁ and Output₂) and theassociated phase angles (Θ+α)° and (Θ+β)° output voltages (e.g., Output₁and Output₂) of the core windings 44 and 46. The process 52 may thenconclude with the one or more the current sensor interface modules 28,30, and 32 and/or other processing devices (e.g. included as part of theone or more sensors 16, 18, and 20) correcting (block 60) one or moretemperature-based and aging based errors and/or distortions in theleakage current measurements (e.g., leakage current signals {right arrowover (I_(a,l))}, {right arrow over (I_(b,l))}, and {right arrow over(I_(c,l))}) based on the calculated first and second phase-shift anglesα° and β° associated with the windings 44 and 46 and the magneticpermeability value of the core 42. Specifically, one or more correctionsfactors may be generated. As previously noted above with respect to FIG.3, in this way, the sensor 16 (or sensors 18 and 20) may provideaccurate measurements of the leakage current signals {right arrow over(I_(a,l))}, {right arrow over (I_(b,l))}, and {right arrow over(I_(c,l))}, for example, irrespective of the ambient and/or operationaltemperature and age of the sensor 16 (or sensors 18 and 20) and/or themechanical stress of the core 42 based thereon. Furthermore, the currentsensor interface module 28 (or current sensor interface modules 30 and32) may provide an indication as to whether the detected leakage currentmeasurements (e.g., leakage current signals {right arrow over(I_(a,l))}, {right arrow over (I_(b,l))}, and {right arrow over(I_(c,l))}) includes capacitive leakage currents, resistive leakagecurrents, or a combination of capacitive leakage current and resistiveleakage current.

Technical effects of the present embodiments relate to a two-windingconfiguration current sensor that may be used to provide accuratemeasures of detected leakage currents by, for example, correcting andcompensating for the ambient and/or operational temperature variationsof the sensor and/or mechanical stress on the core of the sensor. In oneembodiment, the sensor may include a high sensitivity currenttransformer (HSCT). Specifically, the sensor may include a first set ofwindings with a first number of turns and second set of windings with asecond number of turns. The first set of windings and the second set ofwindings may be coiled independently on the core of the sensor, suchthat the sensor provides at least two voltage outputs. In oneembodiment, the two outputs may be connected to the input of a signalconditioning circuit with a multiplexing functionality to ensure thatonly one signal of the two voltage outputs of the sensor is electricallyconnected and processed per time period. Based on the two voltageoutputs (and other measurements obtained by the current sensor and highvoltage sensor) and the parameters of the sensor, the respectivephase-shifts corresponding to the first set of windings and the secondset of windings and the instantaneous permeability (e.g., correspondingto the immediate ambient and/or operational temperature) of the core ofthe sensor may be calculated and used to compensate for, or correct anyerrors that may have become present, for example, in the detectedleakage currents. Moreover, based on the two voltage outputs, and, byextension, the respective phase-shifts of the first set of windings andthe second set of windings, an indication as to whether the detectedleakage currents include capacitive leakage currents, resistive leakagecurrents, or a combination of capacitive leakage currents and resistiveleakage currents may be provided.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

The invention claimed is:
 1. A system, comprising: a sensor configuredto detect an electrical leakage current associated with an operation ofan industrial machine; comprising: a core; a first winding encircling afirst portion of the core, wherein the first winding comprises a firstnumber of turns, and wherein the first winding is configured to obtain aset of electrical current measurements associated with the operation ofthe industrial machine; a second winding encircling a second portion ofthe core, wherein the second winding comprises a second number of turns,wherein the second winding is configured to obtain the set of electricalcurrent measurements associated with the operation of the industrialmachine, and wherein the first number of turns of the first winding isnot equal to the second number of turns of the second winding; whereinthe first winding and the second winding are each configured to generaterespective outputs based on the set of electrical current measurements,wherein the respective outputs are configured to be used to reduce theoccurrence of a distortion of the set of electrical current measurementsbased on a temperature of the core, and wherein the sensor is configuredto transmit the respective outputs to a controller coupled to the sensorto calculate a phase-shift angle and a magnetic permeability valuecorresponding to each of the first set of windings and the second set ofwindings.
 2. The system of claim 1, wherein the first number of turns ofthe first winding and the second number of turns of the second windingcomprises a ratio of approximately 3:2 or approximately 2:1.
 3. Thesystem of claim 1, wherein the sensor comprises a high sensitivitycurrent transformer (HSCT).
 4. The system of claim 1, wherein the corecomprises a high-permeability magnetic core.
 5. The system of claim 4,wherein the high-permeability magnetic core comprises, high nickel,iron, a supermalloy, or any combination thereof.
 6. The system of claim1, wherein the first winding and the second winding are configured tocouple to a signal conditioning circuit, wherein the signal conditioningcircuit comprises a multiplexer configured to transmit the respectiveoutputs one at a time for processing.
 7. The system of claim 1, whereinthe first winding and the second winding are configured to operateindependently with respect to one another.
 8. The system of claim 1,comprising a second sensor configured to detect an electrical voltageassociated with the operation of the industrial machine.
 9. The systemof claim 1, wherein the industrial machine comprises a synchronousmotor, an induction motor, or a generator.
 10. The system of claim 1,comprising a second sensor and a third sensor each corresponding to arespective conductor coupled to the industrial machine, and wherein eachof the second sensor and the third sensor comprises a respective firstwinding and a respective second winding.